1. Field of the Invention
The present invention relates to a linear motion guide unit with lubricating means, which is applicable to industrial robots, semiconductor manufacturing apparatus, machine tools and the like to lubricate the relatively sliding parts and components.
2. Description of the Prior Art
The linear motion guide units have been conventionally used incorporated in the parts or components for reciprocating motion in fields as diverse as the industrial robots, semiconductor manufacturing machines, inspection instruments, machine tools or the like, and further developed to answer the needs for precision, high-speed, miniaturization or the like. The recently remarkable development in mechatronics technology extensively requires linear motion guide units that may meet with needs of maintenance-free, especially, the self-lubrication of long service life on its relatively movable sliding areas, along with miniaturization, high precision and high speed in operation.
FIGS. 14 and 15 show an example of prior linear motion guide units.
The linear motion guide unit in FIG. 14 is primarily comprised of a track rail 2 and a sliding element, or a slider 1, riding the track rail 2 astride for sliding movement. The track rail 2 is formed on lengthwise side surfaces 3 thereof with raceway grooves 4. The slider 1 may move on the track rail 2 by virtue of rolling elements running through the raceway groove 4. The track rail 1 has on lengthwise upper surface 14 thereof openings 13 spaced from each other. The track rail 2 is fixed to a mounting base 20 such as beds, platforms, working tables or the like by screwing bolts through the openings 13 of the track rail 2 and matching openings in the mounting base 20. The slider 1 has a casing 5 movable with respect to the track rail 2, and end caps 6 attached to the opposing ends of the casing 5. Provided on the upper surface of the casing 5 are openings 19 for fixture to mount other appliances, parts or the like on the slider 1.
Both the casing 5 and end caps 6 are made on the lower surfaces thereof with recesses 10, where the casing 5 and end caps 6 may sit astride the track rail 2 for free movement. The recesses 10 are each made with raceway grooves 9 in opposition to the raceway grooves 4 on the track rail 2. The rolling elements 7 contained in the casing 5 run through load areas of raceways defined between the confronting raceway grooves 4 and 9. Retainer bands 18 are provided in the casing 5 so as to embrace therolling elements 7 to thereby prevent the rolling elements 7 from falling out of the casing 5. Bottom seals 8 are affixed to the lower surfaces of the slider 1 for closing clearances between the track rail 2 and slider 1.
The end caps 6 are provided therein with members for scooping up the rolling elements 7 from the raceway grooves 4 on the track rail 2, and turnarounds for circulating the rolling elements 7. Mounted on the end caps 6 are end seals 17 for ensuring the sealing performance between the track rail 2 and the lengthwise opposing ends of slider 1. The end caps 6 are connected to the opposing ends of the casing 5 by means of bolts 21, which are screwed into their matching holes. The raceways defined by the confronting raceway grooves 4, 9, turnarounds formed in the end caps 6 and return passages 12 formed in parallel with the raceway grooves 9 in the casing 5, in combination, constitute endless-circulating paths for the rolling elements 7. Even though the rolling elements 7 are under loaded condition in the raceways, rolling-contact of the rolling elements 7 with the raceway grooves 4, 9 may help ensure the smooth movement of the slider 1 relative of the track rail 2.
To lubricate the raceways where the rolling elements 7 run through, grease or lubricating oil is usually employed. In case of grease, it is applied to the raceways through grease nipples 11 that are mounted to the end caps 6, extending through the end seals 17. In contrast, lubricating oil is supplied to the raceways through pipe joints, which are used substituting for the grease nipples.
Japanese Patent Laid-Open No. 205534/1998, which is a senior co-pending application, discloses a linear motion guide unit having for its object to provide a maintenance-free lubrication system for the raceways, as shown in FIG. 15. In the linear motion guide unit cited above, lubricating plate assemblies 15 having lubricant-containing members are attached over each outer end surface of the slider 1.
The linear motion guide unit in FIG. 15 is substantially identical in structure with that in FIG. 14. To that extent, like parts or components have been given the same reference characters, so that the previous description will be applicable.
Attached on the casing 5 of the slider 1 by the clamping bolts 21 are reinforcing washers 16 and lubricating plate assemblies 15 having therein lubricant-containing members, along with the end caps 6 and end seals 17. The reinforcing washers 16 each are of a steel plate formed into a substantially inverted U-shape, which is fit to the outward contour of the end cap 6. The washers are arranged in no contact with the track rail 2.
The lubricating plate assembly 15 is also formed in a substantially inverted U-shape, which is fit to the outward contour of the end cap 6. The lubricating plate assembly 15 includes therein the lubricant-containing member made of sintered resinous component. The lubricant-containing member is provided on the inside thereof with convexities, which are formed in adaptation with the cross section of the track rail 2 so as to come in sliding contact with its associated confronting raceway groove of the track rail 2. For constant supply of the lubricant from the lubricant-containing members 15 to the raceway grooves 4 on the track rail 2, the lubricant-containing members 15 are forced against the raceway grooves 4 on the track rail 2 by spring effect of resilient metal casing covering around the outer peripheries of the lubricant-containing members of the lubricating plate assemblies 15.
Application of lubricant from the lubricant-containing members of the lubricating plate assemblies 15 onto the raceways of the track tail 2 has an advantage of providing the self-lubrication system in which the raceways defined between the confronting raceway grooves 4, 9 of the track rail 2 and the slider 1 are kept in maintenance-free for lubrication continuously whenever the lubricant is supplied. After the lubricant has been consumed, the lubricant-containing members in the lubricating plate assemblies 15 may be replenished with other lubricant to thereby prolong the service period to the next chance of replenishment.
Other linear motion guide units with lubricating plate assemblies have been developed and disclosed in, for example, Japanese Patent Laid-Open Nos. 82507/1999 and 93952/1999, which are senior co-pending applications.
Moreover, Japanese Patent Laid-Open No. 126235/1997 disclose a linear motion guide bearing-unit having lubricant reservoir means made of a rubber or synthetic resin block containing therein lubricant. The lubricant reservoir means is attached to the linear motion guide unit by connectors to apply continuously the lubricant for a prolonged period of service life, as the slider moves along the track rail by virtue of the rolling elements. The lubricant reservoir means is, for example, arranged between two juxtaposed sliders so that the lubricant reservoir means is forced alternately in opposing directions by means of either one of the sliders to move along the track rail, whereby the lubricant oozed from the reservoir means may be applied little by little onto the track rail to lubricate the rolling elements of the linear motion guide unit.
Disclosed in Japanese Patent Laid-Open No. 184683/1998 is lubricant-supply means having lubricant-supply members that are mounted on sliding members so as to apply the lubricant to the surface of a guide shaft. The lubricant-supply member is comprised of a lubricant applicator contained in a casing, a lubricant storage arranged adjacent to the lubricant applicator so as to hold the lubricant therein and feed the lubricant to the lubricant applicator, and control means of a flow adjusting diaphragm to regulate the amount of lubricant to be fed from the lubricant storage to the lubricant applicator.
Nevertheless, as the linear motion guide units become recently more common in diverse fields of wide applications, they are increasingly used under unfavorable operating conditions or adverse environments, where the replenishment of lubricant is made even tougher. In recent years much attention has been thus given the development of the linear motion guide units that would be long-lasting as for maintenance-free with no replenishment of lubricant. For prolonging the service life available for the next replenishment of lubricant, it may be considered to render the lubricating plate double or triple. Nevertheless, the design has drawbacks of making the lubricating means large in size as well as expensive in production cost.
Thus, even if the lubricating means may be made compact in size by assembling together both of a lubricant-storage and lubricant-apply components into a single case, it will be expected to render the lubricating means miniature while ensuring a enough storage capacity for lubricant, which makes it possible to provide the prolonged period of maintenance free as for lubrication.